This communication reports a quantitative study of levels of S-adenosylmethionine and S-adenosylhomocysteine in pea seeds during the first 3 days of germination. There is net synthesis of both compounds during this period. The S-adenosylmethionine, which is in an active state of turnover, is formed from activation of methionine. Isotopic studies indicate that other recognized pathways of S-adenosylmethionine biosynthesis are unimportant in germinating pea seedlings.